The positive trait of Happy is obvious...happiness, joy. A negative aspect of Happy might be excessive happiness or sheer lunacy. Not a survival trait.
The negative trait of Sad is obvious...sadness, but sadness is the nucleus.
My shadow portends when survival is the goal there exists cosmic balance. Excessive sadness becomes the negative.
Excessive sadness is not a survival trait, not a negative of happy, but a negative trait of sad.
Next my shadow discusses the concept of free.